1. Simple Machines in Technical Theatre
USITT 2008
Simple Machines in Technical Theatre
Levers
Chip Haas – Technical Director, University of North Carolina Greensboro
Drew Pritchard – Technical Direction Student, North Carolina School of the Arts
USITT 2008 – Houston, Texas

2. There are three classes of levers: Class 1, Class 2 & Class 3.
All three classes have the same three components
1. Fulcrum (‘F’) – the pivot point
2. Load (‘L’) – some kind of weight or resistance
3. Effort (‘E’) – the force that is trying to move the load
The differences lie in the location of these components
Remember: ‘F’ always proceeds ‘E’, ‘L’ is the only part that moves.
USITT 2008 – Houston, Texas

3. Class 1 Lever – ‘LFE’
Fulcrum is located between the load and the effort
The longer the effort arm (D2), the less force necessary to move the load
Effort Arm(D2) / Resistance Arm (D1)= Load / Effort
USITT 2008 – Houston, Texas

4. Common Class 1 Levers
USITT 2008 – Houston, Texas

5. Class 2 Lever – ‘FLE’
Fulcrum is located at one end and the effort is located at the other end of the lever
The load is situated somewhere between those two points.
The closer the load is to the fulcrum, the less force necessary to lift the load
Effort Arm(D1 + D2) / Resistance Arm (D1)= Load / Effort
USITT 2008 – Houston, Texas

6. Common Class 2 Lever
USITT 2008 – Houston, Texas

7. Class 3 Lever – ‘FEL’
Fulcrum is located at one end and the load is located at the other end of the lever
The effort is situated somewhere between those two points.
This allows the load to be moved faster, however the effort must be greater than the load
Effort Arm (D1) / Resistance Arm (D1 + D2)= Load / Effort
USITT 2008 – Houston, Texas

8. Common Class 3 Levers
USITT 2008 – Houston, Texas

9. Failed Use of a Class 1 Lever
Pop Up Door – Down Position
Pop Up Door – Up Position
USITT 2008 – Houston, Texas

10. Problems with this attempt at a lever
Effort arm is shorter than the resistance arm
Made door even heavier to lift – solved using counterweights
Trapdoor platform behind effort arm prevented any extra length to the effort arm
Door Flat too close to end of resistance arm
Couldn’t move high enough – 9” too short
Angle of arm became too steep to keep raising door
Couldn’t extend resistance arm, not enough room
Couldn’t raise fulcrum – structural steel in the way
Door wasn’t heavy enough to come back down, unable to attach lever to pull the door down.
How was it solved?
- Made it even simpler – eliminated the lever - had crew member raise and
lower like a window
- Not quite as smooth – locking mechanism was kind of jury rigged
USITT 2008 – Houston, Texas

11. Use of a Class 2 Lever – ‘FLE’
Effort
Load
Fulcrum/ Pivot Point
Example presented is a pivoting wagon unit which is attached to a pivot point.
The pivot acts as a fulcrum, the scenery and people on the unit act as the weight, and the actor moving the unit acts as the effort.
When moved from the end opposite the fulcrum, it acts as a class 2 lever
Effort Arm(D1 + D2) / Resistance Arm (D1)= Load / Effort
USITT 2008 – Houston, Texas